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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84a1a6fad3289720f0c664bc9db261dd24f147e9aac2d0e0fd7f7cda80ff1c4e' 
  AND token = 'eJ0/9HS0nBwZKT5XO8dPG/YwJQRdgy89+3Cil4oXCDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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