SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1a37c87c1a52361ae29da0ca4036b3e9b54941b241073f92375c43587a44875c' 
  AND token = 'eR5Wprz5gidlPbNdJlQqOpzvDhfx7aBvPjgvAiVzVGM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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