SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe44b01eb8c072ee553cbc77c7967f87ade12cfcdc537740e03b749ec253121c' 
  AND token = 'S4J48oEA6t/Ei1kRRwPB6xQFIyCC8aMZ3rRnxAkmrMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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