SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79909372260247a7978c90512ea19d7c2a1b40342b06a019a9658270c139c378' 
  AND token = 'fYC+GR1ukhqBifhBLieNhDKxAGfLEXtGNmgYNRX7U4w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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