SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c31e9bce62770171c8015607b8ae90b2a543e89f021c027f0607b2780805355' 
  AND token = 'qz81QoTEt2I+g+hzpS5ZiuhG3Q5P4BKJYhv3AhSumHo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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