SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f655bafd8a57ae4f47397168eb11859c6e26c9b8a94f12efa32b88e40a9e75' 
  AND token = 'nOsVu1ZgZDmtefPtlNnpcOfVsOeFhU1k+2z2WkS+MjU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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