SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac69be5fec444aa16515cb738607df9a8e1dca7d24a592091813cf6723401581' 
  AND token = 'CTjiQ825F2ZF2oOQSbmuSH4oQCuu96djAclEQBWTBrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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