SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3c8d2a939690e8a6fce301756fbb1c511e67c5cb92bd51b1740a17a9436f2ea' 
  AND token = 'mqs3rYmYvZqB2vyIu/l0zM79PNVfxbQ/4rwASdUvw9w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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