SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3cc998c4f0227e89d7c5d2f5584b8fa3676a352d648cb3a3d85d72b759bfbbd' 
  AND token = 'T6dBRWgnSoAkZKMuiDDoCYh9oFxgsZz7YcEwqPsT2JE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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