SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9e6789ba080046a03a1ab6975021729ac6b711a11b1ab76969a3d7db2da89d6' 
  AND token = '6BoQMchOR+ylp0mRhyy7FgeyY1SN2Zusb43rGeqQqys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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