SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68d0d1b1722725dddf26c5e84b1f9e329602500fe813a44fc99bc45ba3a287c3' 
  AND token = 'jXOUvGpzLeKGrnQzFc6pMIkRbSqzqtmmWVNS1j+y9UU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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