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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4642ad4df26f7e9b9226bce1836fc19452bcf73bcc100024294b8ecb0d725eb' 
  AND token = 'bcuPWCjt/+hpSl1loZf47MfAm4321u/4MXbBLgL9+x4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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