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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d8df3f03bdd7b809f54d461f7c790c9c527f44b43341998171e1f565dde4e57' 
  AND token = '9Zdf2FZfbQEPo9c61kj3Rgsml1GyPIgpn6DMqK+7T9s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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