SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc76da2e78ed2a3c291d9e60737a684140e80e798d0612983778d6f2619e6974' 
  AND token = 'yEk3KGmV0UVH+4ZfqFQYKyiOylseHC0ll42oUSdAXS4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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