SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3188841552d6afd5c1f8abd520368aa93e64e6550d22f01cdeeddf73b2d9256f' 
  AND token = '5STwnGJEnskbbQMGBbfXYYJKHeWfzmg/k0PuGp67S3k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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