SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b3694cf6d5ee88451a2607615714bf6443971faaf5b3cad7d7c9837d3d76955' 
  AND token = 'aJ1VdcZrSotptT1RLzNPCNHdzrHVvaj0FNBeAlM4zEo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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