SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '621287413447944b69d2433f2080a78c1f9f2824c187e4ab70c9d694050d2d84' 
  AND token = 'tUnlutBjkJTjY1LG/L6m0ATtdl0OXhKHVmHGjvQRS28=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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