SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2749b07257ea042eb282ace13076200e5e96764bc933a2c3fc8684fecbee8d1' 
  AND token = 'JJ+pTaalEMKBIZ/LSmIR7qWm1wULIhiY7KBy/FYo92g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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