SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e07683390ab7aff04c654f882974ed615b1416d0b9208461d784e83cd331cb' 
  AND token = 'TbO8Bl/B3tD4xS/jZk+EkTQHJPIZWHWkUsJTw5e+iMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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