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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '399e4e8a6419dadec9bdfcb4e36359549fda0a10b6e9a751dc83bd5280beaa91' 
  AND token = 'S1VIs9y9F/Y7oXmE4JsDfVn+u2xfXSwyWVzZ4dv/OrM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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