SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0c50022ac73c769ab2b12af8c427186043a51fd83edbd11d0846bc0499ebbec4' 
  AND token = 'lBd75ZmlRIlTdxfhg5UQ+tGxLF2HXag9E1wJiqv1rGY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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