SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '57fcd4960add724a273dd8cbdd266c374f6da1d1dfaa18198170371fcb64bbf2' 
  AND token = 'P9mFcJYxMAqLEmEgyZg9/X7ui0Dc4H0tzuaBcHgfQ0Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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