SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55f7bb103cb8b4f79606b86d250957a7c4c7f4879dfff11779af44275a1b76db' 
  AND token = '889PKUDLZVj/XQDkmQHt7h1+xp1/fuXGowW3vrDbwa4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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