SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a74ef87ed9f479035bec856f460f8f4096419b321cc1da905982034d79f91023' 
  AND token = 'b//mMGaLTbI158PLw0USeW0Tpj5/ktfooUCqOIv+wpk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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