SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '776a0a764db600a786191f9150f07f025864549b729e76c23aac1eab942f1d39' 
  AND token = 'PJOkWtXBYOaZW2nGjtOCbnzKUrXJrlZrFDOnp+oz1p8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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