SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6f6e292664ba22bcdecd7fb8a8ef1ee970463f84bbb8ba22b0847e478ff1489' 
  AND token = '/iEFs0OUREGSsL8+TiUkCBVyw4iNe/MxN9oExQkIyxQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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