SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ffcdb720392c39b3f4aa22fd771aaf03f78618734b17976150179297b0bd8ad' 
  AND token = '1SWfhk+GtjKodLHzhycSRZlvZa/aXB8wmz8kft+maZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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