SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8a1423886ccff60b4a07d06f1fcbb939fd7b548e646a49bff22e440b83dc784' 
  AND token = 'B9XO9A4vnVorn2zy7knKBobh1/w3q6lyDgGsvPQipME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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