SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c2702dea85ab45254a48f4060a5469826b782f57ecf025b217f936000c83896' 
  AND token = 'z7dcPf7e1GqZpfzMPE6MxH0pmpGhUvFAzMvFtut6mZw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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