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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c740d9ab4ac5ddf8e4aff4b4de7df997dbdd2703afb1d3b19a5da596ad6175f3' 
  AND token = 'DXRPky+LSauVWDdd5JcY2uJZFGGly/Czb11w7bznqRM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}