SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c135885ab799333264d771b51f888d00a343848f26ee391df2e83af40f5a2c58' 
  AND token = 'e8d6umYOi6ckRux+A3aPGqLuBVilq8LS93h2PrMzS+U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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