SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7b9c91b0a9606493b300205a1c2d7161f29b5420709edfbb5dbf8faf37546fc' 
  AND token = 'cgUZfdx1mnVeo8icshhRynjjVTCq+43JvAKWvRtt4kQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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