SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39f9fe0cfb805128ce1ec88d4291dc502294873cb7e0a44ca224da1cae74eb38' 
  AND token = 'CUBFLFW1MkbulbdjmIxsuAW3CsXrIpkyrYR3c86ToBw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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