SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e256489c9011edb4cb538f56c79f64780d64536962ec863244a8deef451d9ebc' 
  AND token = 'x9y0pQcZ6p1tZSCaRMuQGJtuV+KVglqV9OQJ2t/9yKs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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