SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dd50826b37622f5dac8a93847dd4ac2cebd7835b5e285b59c80923689a549f1d' 
  AND token = 'G28ejz9z+bQYnp1tdrWUVfomEnMrpKADonFA1RCeuwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00057

JSON explain

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