SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71102bace978dfb80bed282d6244e3349aaca1398254433c1ca438d55dcce52c' 
  AND token = 'llF1tPzhjlAhqujlaecpDviYBUsLgeGBJGGqg7E45To=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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