SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '426e505244f1a1faff2541800b961314f3143342b43d9759540de179f0a9c3ad' 
  AND token = 'pkyxVA8sEyohyhmkqEQ7p75y+jytSbu6dGhZ/BBd8zQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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