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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b346be932b68f5ca76cab36790ce2b3a41459bdd9cc5d2c53bf231c6ee37c948' 
  AND token = 'u3dmYobm9Ym55pHEQCZ3lDRB4KaRAW+DCOQv3ZuHBPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}