SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ebac161a8e78dadcee349338466a4c923391c8421488e61c58e19335ce5aac8' 
  AND token = 'KE31AMpUB75aFctArzPSlowwGT7hC+qQy2Q/hlbOmkc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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