SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '837a6ab691a7811848317d081c82ec33032a41779595a1b4009c3da6d4dfa854' 
  AND token = 'uUij0emKlVGFg3tSZfPtvFTrp2VeU8LSDVVlccQshYc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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