SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b403354a77a7b9ed2d97c1b100c73378f2459f870e49b4b98fb71161c7b28464' 
  AND token = 'L6otdtbjmg7DVKAWjNRcyJfc0rOAgcsyEACvTeWXoOY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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