SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b795af3cf7032beb68297596977436a4673e934dcc982f205efd3526be4871d5' 
  AND token = '6FZWcI5JOjot5ig6PCf/KfDDQRbcxYNH+BlCaE3vz8I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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