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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '608764765232aa7a7858c623fa3223a1e08e472bebd0273662d67dca94a100af' 
  AND token = '978pAlCB2zGI4IJlq1/+Ev4S5Wt1rEvA/bbiEtvte7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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