SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8dcbc8767a6154763bb23fcea950925b3ddc0f24815e79799bff1dd3f89878bb' 
  AND token = '9jQInwSS/5uBlrmB6Qeq3mxMhVgMqMEXgWnhF9eqVQs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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