SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7cede1cafb451a76c9e10f14491bbf4c68e120509ac3b0f438ba379b6ab3b304' 
  AND token = 'DPk4XKsHMflRZSLRD/MJP0efYVms63qukut1fL9drAY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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