SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d5b50ca9f6a088f25b2e524b6e6f54d0438991306af60aac6803e199964f6d7' 
  AND token = 'GJOEOgQ3QDGNk7+TbUuJKFqE+RHk5F/RNcGYQclKdMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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