SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8181c408a3ecb7593b11b393b0c3a7c36e6dea373481079ccb4a98f0cb75d75' 
  AND token = 'OSSe82XMIfYv6aodOnfWcqFepOFNfJJms31sAnc60iM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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