SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e235db5634684437a8fd748c30bf327495517ee61f445f891e5c5d343fa976e4' 
  AND token = 'T+MVA/BDcLRP67MTKdqGD9fBydh9lFVcCHMUzkpOWgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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