SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff750afbed89ab3f138dd4c8251a3f2caae781c68bb379c5231538a9aeab4fe9' 
  AND token = 'LP3eGhqJ2u4yY+TPvWlyR6nkIwD8NpHR/ZYx2Auncmo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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