SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39f5485db3183f65b3be9f6c50537403ecf32a243e19ed1c47dd4a40aad709da' 
  AND token = 'GfHMUmKcK/BBpZo31V5vXjPlKZnBLDHMj+sjama2Afk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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