SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68e51ed294c664de8ff3170e5e81b58851e47dea89060193051c57360fd440db' 
  AND token = '1BgAqNbaKcpjNxMeY1GfEuBcMVMIE7UYSNrvM+DT6Xw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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