SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '734136792a221edb0d140a6436495749142e63b05910f967ac20a98bdc66ae99' 
  AND token = 'Z4g4YNMfQQUuv941Q4uss28uoyWqBEwYbqBdYq3yvkY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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