SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2d316667ee2ce979d0f5478eab51499744c490a30eb84e7c8b043a940a3a877' 
  AND token = 'py480TanihyJplf4Do3Pepx6o97YrF6JOOwMJIzHqsA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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