SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '08b76896be5dddde74901f321015f960e766315795cb8d00fd19933631d14bf1' 
  AND token = 'aeKIgJ9tc+mTWb6MQxERMHZSNlZIxLR/Abz45hpqFd4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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