SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2ded23fc312808cc3e4400c49b3d2e4ff9e3d603fb4111f0643056761fb64cc' 
  AND token = '0kaMcj7oFZCM2CtI53IXVzWRydBu/Cf1SumCNpU+oCo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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