SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '511d0d3b938ec4f42b9fd1840a068c1a2e3280cebfd3114c887d1dd77d5986ae' 
  AND token = '6RZW0BjYPJphO2CQYLIAQWIVKmWXPg8gEfKaajSIk6M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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