SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '397a11da6b241cbaa799f7774ec87d44a299062f2a25bc8741c0a75d1f4e5dd4' 
  AND token = 'LhrYLmcJNOWSz8mMfBRFm47qB7uYnuz/HzyXehQO8Hw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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