SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '92850c3fc1540fab38f15b06c8b02a2c7dc6455243050d278fef7327d4da27b2' 
  AND token = 'lJtbMnZyRLYFKdNtxSFsuwIqX1F0qwCMDkw7pO9i0w4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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