SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6bcdc7b3bdbca610781541bbffd958a5f9f256592e47602188250e41cb7fd445' 
  AND token = 'fk/FdZgYrzWexcp5s/29+sFwpHsJMjQbsrmJWwhHbso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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