SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fec0cebd69bb60dc6d6e48909befe0d9f2fa43902441caadaadcbc0b4c803a0c' 
  AND token = 'pHiujxNqQ2TtEmNoFn11mz2mdY+5GjJroJ4sSwWpPvU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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