SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e799a764facf64f384decb4a8133accbbdb4bff53c1290e796756eac1ee6b08' 
  AND token = 'xR+0V2LG/KMlmoK0bgvB+FSCmVunJ3xt572lkYUAoyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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