SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6c58c64eba5f8df207628f8d304a51f877eb45a04b68f647c79412ae08e3294' 
  AND token = 'ZEQeAKQcmI12DEHWRZTD8diNRF6YhmBQzcRThQwcg1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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